1. Technical Field
The present invention relates generally to continuous casting furnaces. More particularly, the invention relates to a continuous casting furnace having a temperature control for controlling the temperature of the metal casting produced via a continuous casting mold of the furnace. Specifically, the invention relates to such a temperature control which includes a temperature sensor, a heating source and a cooling source for controlling the temperature of the metal casting in order to provide improved characteristics of the casting.
2. Background Information
The principal of continuous casting is to pour molten metal into a water-cooled copper mold and continuously withdraw the solidified metal out of the mold to form a cast ingot/bloom/billet/slab. The continuous casting process is widely used for making steel casts, the direct chill casting (DC casting) process for making aluminum, copper and nickel base alloys, and the electroslag remelting (ESR) process for making nickel base superalloys, tool steels and stainless steels. The cast bloom/billet/slab during the continuous casting of steel can be cut in specified lengths and removed. Thus, the casting process can, in theory, continue indefinitely. On the other hand, DC casting and ESR processes are used to cast a finite length of ingot/billet/slab. Thus, they are commonly referred to as semi-continuous casting processes.
For both the continuous casting of steel and semi-continuous casting of non-ferrous alloys, the temperature control of the cast ingot/billet/slab is a crucial factor to ensure a smooth operation of the casting process. Water spray is commonly used to speed up the heat removal of the metal casting, resulting in a fast cooling rate and a reduced degree of macrosegregation in the resultant ingot/billet/slab. For a moderate cooling effect, forced air cooling can be used. However, for the casting of segregation-prone and cracking-prone alloys such as tool steels, an insulation blanket is sometimes used to cover the surface of the cast ingot and slow down the ingot cooling rate. This results in a reduction in the temperature gradient, residual stress and cracking tendency in the cast ingot.
Plasma arc melting (PAM) and electron beam melting (EBM) are two semi-continuous casting processes commonly used to make titanium alloys and, to a less extent, nickel base superalloys. PAM is performed in an inert gas (Ar or He) environment whereas EBM is performed in an environment under vacuum. For both processes, the furnace chamber is sealed from outside air atmosphere. Thus, the methods of water spray and forced air cooling cannot be used in PAM and EBM for controlling the ingot temperature.
The current invention is an innovative method to control the temperature of a continuously cast ingot, certain aspects of which are particularly useful in an inert gas or vacuum environment. Such temperature control provides improved characteristics of the metal casting such as surface smoothness and internal metallurgical structure, which are strongly dependent on the temperature distribution within the ingot.